The present invention is related to a power ratchet wrench, and more particularly to a mechanism for controlling circuit-closing/opening of a power ratchet wrench.
A conventional power ratchet wrench has an elongated tubular main body in which various components of the power ratchet wrench are accommodated. Referring to FIG. 1, a user's hand can hold the main body to operate the power ratchet wrench 1. In operation, the user's thumb must always press the circuit-closing/opening press key 2 for closing the circuit to power on the driving unit inside the main body. When releasing the press key, the power is cut off.
In actual operation, the power ratchet wrench is often operated at high torque and high rotational speed. Under such circumstances, it is inconvenient for a user to hold the power ratchet wrench due to improper design of the circuit-closing/opening press key.
In order to stably operate the power ratchet wrench, a user's hand must tightly enclose and hold the main body of the power ratchet wrench. However, the user's thumb always needs to press the circuit-closing/opening press key. Therefore, the user's hand can hardly fully enclose the main body of the power ratchet wrench. Accordingly, the user's hand can hardly firmly hold the power ratchet wrench. Consequently, it often takes place that the power ratchet wrench jumps out of the user's hand due to shock in operation.
U.S. Pat. Nos. 6,923,095 and 5,195,406 disclose a control valve structure for closing/opening airflow passage of pneumatic ratchet wrench. Such control valve structure enables a user to more firmly hold the pneumatic ratchet wrench in operation. However, no similar measures applicable to power ratchet wrench have been disclosed.